KR20060103923A - Optical disk unit - Google Patents

Abstract

An optical disk unit, wherein the transmittance and reflectance of a polarization beam splitter (13) with respect to the S-polarization and P-polarization of a laser beam are adjusted such that the first polarization component level ratio of a laser beam received at a signal reproducing photodetector (17) from a laser diode (11) via a polarization beam splitter (13) and the second polarization component level ratio of a laser beam received at a light source monitoring photodetector (18) from a laser diode (11) via a polarization beam splitter (13) agree with each other or the difference between the first and second polarization level ratios falls within a specified allowable range.

Description

Optical disk unit

The present invention relates to an optical disc apparatus for using an optical disc such as a DVD (Digital Versatile Disc) or a CD (Compact Disc) as a recording medium, and recording or reproducing information by irradiating a laser beam to the optical disc. In detail, the present invention relates to an optical disk apparatus for removing noise components of a laser light source.

In optical discs such as DVD and CD, since the signal to be handled is analog, the demand for light source noise is very difficult.

On the other hand, the return light noise and the mode hopping noise exist in the noise generated by the semiconductor laser used for recording and reproducing the information on the optical disk, and both of them seriously interfere with the reproduction signal.

This return light noise causes a part of the beam reflected from the optical disk to return to the inside of the semiconductor laser, so that the optical disk acts as an external reflector, causing mode contention between the original internal resonator and oscillation in oscillation. This is the result of occurrence. In addition, mode hopping noise is noise generated when the longitudinal mode changes as a result of the resonator length of the semiconductor laser itself fluctuating due to temperature change or the like.

In the optical disc recording and reproducing apparatus, there is a problem that the laser noise increases due to the return light from the optical disc or the temperature change of the semiconductor laser, which adversely affects the reproduction signal. As a method of reducing the laser noise, there is a laser noise canceling (LNC) method that cancels the noise component of the laser beam directly monitored from the optical signal modulated by the optical disk (for example, Japanese Patent Laid-Open No. 2002-352459).

4, a conventional LNC optical disk device will be described.

In FIG. 4, the optical head portion 40 includes a laser diode (LD) 41, a collimator lens (CL) 42, a polarization beamsplatter (BS) 43, and a quarter wave plate (QWP) ( 44, an objective lens (OL) 45, a condenser lens 46, a signal reproduction receiver (RFPD) 47, and a light source monitor receiver (FPD) 48.

In such an optical disk apparatus, the laser light emitted from the laser diode 41 enters the polarization beam splatter 43 through the collimator lens 42. Part of the laser light that has passed through the polarizing beam splatter 43 is converted into circularly polarized light through the quarter wave plate 44, and is then focused on the optical disk 50 by the objective lens 45. After the laser beam is modulated by the recording information of the optical disk 50, the laser beam passes through the objective lens 45 and the quarter wave plate 44 again, and is linear in the quarter wave plate 44. The light is returned to the polarized light, enters the polarization beam splatter 43, is reflected by the polarization splitting surface, and then enters the signal receiving receiver 47 through the condenser lens 46. On the other hand, a part of the laser light emitted from the laser diode 41 is reflected by the polarization separation surface of the polarization beam splatter 43 and is incident on the light receiver 48 for the light source monitor.

Further, the optical signal detected by the signal reproduction receiver 47 and the light source monitor receiver 48 is converted into an electrical signal, and amplified by the amplifiers 51 and 52 so that the noise level is the same. The arithmetic circuit 53 composed of a differential amplifier circuit and the like outputs an LNC signal obtained by canceling only the laser noise component from the RF signal.

Here, since the polarization beamsplatter 43 has a polarization characteristic, and the 1/4 wave plate 44 which suppresses the influence of return light is inserted in the optical path which reads an RF signal, The ratio of the TE wave and the TM wave of the laser light received by the signal reproduction receiver 47 and the laser light received by the light source monitor receiver 48 may be different. In this case, since the correlation between the noise of the TE wave and the TM wave of the laser beam emitted from the laser diode 41 is low, if one of the noises of the RF signal received by the amplifiers 51 and 52 in the signal receiving receiver 47 Even if the level of the component (for example, TE component) matches the level of the noise component of the FPD signal (same TE component) received by the light source monitor receiver 48, all of them can be canceled by the calculation circuit 53. However, the noise of one noise component (TM component) cannot be canceled because the levels are different.

That is, the laser diode 41 shows the polarization direction of the laser light emitted from the laser diode 41, and as shown in FIG. 5, the direction in which the electric field is parallel to the active region layer (perpendicular to the thickness direction of the active region layer). TE mode polarized in the direction of phosphorus) and TM mode in which the electric field is polarized in the direction perpendicular to the active region (direction parallel to the thickness direction of the active region layer). Since noise is generated irrespective of each other, there is a problem that the amount of cancellation is lowered in an optical system having polarization dependency.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above points, and reliably removes laser noise components of two orthogonal polarization components (TE wave in TM mode and TM wave in TM mode) of orthogonality of laser light emitted from a laser light source. We are going to propose an optical disk device that can do this.

In order to solve this problem, in the present invention, an optical disk apparatus having an optical separation element for distributing laser light from a laser light source to an optical disk and a light source monitor receiver, and reflecting the reflected light from the optical disk to a signal reproduction receiver. The first polarization component level, which is a level ratio of a component corresponding to the TE component of the laser light that receives the reflected light from the optical disk from the laser light source via the optical separation element in the signal reproducing receiver and the component corresponding to the TM component. And the second polarization component level ratio, which is the level of the component corresponding to the TE component of the laser light received by the light source monitor receiver through the optical separation element from the laser light source and the level ratio of the component corresponding to the TM component, coincides with each other or The difference between the first and second polarization component level ratios is a predetermined allowable range Adjust the transmittance and reflectance of the S- and P-polarized light of the optical separation element so that the difference between the laser noise component received by the signal reproduction receiver and the laser noise component received by the light source monitor receiver is adjusted. In this way, it is possible to obtain a reproduction signal in which a desired amount of laser noise is canceled out.

As a result, in this optical disk apparatus, it is possible to obtain a reproduction signal in which the TE component and the TM component of the laser light emitted from the laser light source are reliably removed or suppressed within the allowable range.

In the present invention, there is provided an optical disk apparatus having an optical separation device for distributing laser light from a laser light source toward an optical disk and a light source monitor receiver, and reflecting the reflected light from the optical disk toward a signal reproduction receiver. Between the optical separation element, a polarizing element for passing either the laser light TE component or the TM component emitted from the laser light source is provided, and the polarized element is used for signal reproduction of the reflected light from the optical disk via the optical separation element from the laser light source. In the light receiving monitor receiver, the first polarization component level ratio, which is the level of the component corresponding to the TE component of the laser light received by the light receiving element and the level ratio of the component corresponding to the TM component, and the optical source from the laser light source The level of the component corresponding to the TE component of the laser beam to be received, and The laser which receives the light from the light receiving element for signal reproduction after adjusting and adjusting the transmittance | permeability and reflectance with respect to S polarization and P polarization of a light separation element so that the 2nd polarization component level ratio which is the level ratio of the component corresponded to TM component may mutually match The difference between the noise component and the laser noise component received by the light-receiver for the light source monitor is obtained so that a reproduction signal in which the laser noise is canceled can be obtained.

As a result, in this optical disk apparatus, it is possible to obtain a reproduction signal in which the TE component and the TM component of the laser light emitted from the laser light source are reliably removed.

1 is a configuration diagram showing one embodiment of an optical disk device according to the present invention.

Fig. 2 shows the relationship between the noise component received by the signal reproduction receiver and the noise component received by the light source monitor receiver for the TE and TM waves of the laser diode (laser light source) in the present embodiment. It is explanatory drawing.

3 is a configuration diagram showing another embodiment of the optical disc apparatus according to the present invention.

Fig. 4 is a block diagram showing a conventional LNC optical disk device.

5 is an explanatory diagram for explaining the TE mode and the TM mode of the laser light emitted from the laser diode.

[Code Description of Main Part of Drawing]

10 optical head 11 laser diode

12 collimator lens 13 polarized beam splatter

14: 1/4 wave plate 15: objective lens

16: condenser lens 17: receiver for signal reproduction

18 light receiver for light source monitor 19 polarizing element

20: optical disc 21, 22: amplifier

23: operation circuit

The optical disk apparatus in the best form of the embodiment of the present invention is a component level corresponding to a TE component of a laser beam received by a signal reproducing receiver via a optical separation element from a laser light source, and a component level corresponding to a TM component. The component (equivalent to the first polarization component level ratio), the component level corresponding to the TE component of the laser beam received by the light source monitor receiver through the optical separation element from the laser light source, and the component corresponding to the TM component S-polarized light and P-polarized light of the optical separation element so that the level ratios of hereinafter (hereinafter referred to as the second polarization component level ratios) coincide with each other or the difference between the first and second polarization component level ratios is within a predetermined allowable range. The transmittance and reflectance for the light source, and the laser noise component and the light receiver for receiving the light Standing by taking the difference between the laser noise component for receiving and configured to obtain the laser noise in a desired amount by which the offset signal reproduction.

And it is determined by the polarization ratio LDp which is the ratio of the level of TE component and the level of TM component emitted from a laser light source, and the optical element which exists on the optical path between a laser light source and a signal reproduction receiver. And the ratio of the transmittance of the component corresponding to the TE component of the laser beam from the laser light source to the signal reproduction receiver and the transmittance of the component corresponding to the TM component (hereinafter referred to as the first polarization component transmittance ratio) (RFpo) and The transmittance and TM component of the component corresponding to the TE component of the laser light from the laser light source to the light source monitor receiver, determined by the optical element existing on the optical path between the laser light source and the light source monitor receiver. The ratio between the corresponding component transmittance (hereinafter referred to as the second polarization component transmittance ratio) (FPDpo) and the required value of laser noise cancellation amount Na are given by the following relational expression. It was to represent.

Thereby, the laser noise component contained in the TE polarization component and the TM polarization component of the laser light source can be suppressed within a desired allowable range.

(1) Example 1

An embodiment of an optical disk device according to the present invention will be described below.

1 is a configuration diagram showing an example of an optical disk apparatus according to the present invention, and FIG. 2 is a noise component that receives a TE wave and a TM wave of a laser diode (laser light source) according to the present embodiment in a signal reproduction receiver. It is explanatory drawing which shows the relationship with the noise component received by the light receiver for light source monitors.

In FIG. 1, the optical head portion 10 includes a laser diode (LD) 11, a collimator lens (CL) 12, a polarization beamsplatter (BS) 13, and a quarter wave plate (QWP) ( 14) an objective lens (OL) 15, a condenser lens 16, a signal reproduction receiver (RFPD) 17, and a light source monitor receiver (FPD) 18.

In addition, amplifiers 21 or 22 are connected to the output terminals of the signal reproduction receiver 17 and the light source monitor receiver 18, respectively, and the output signals of the amplifiers 21 and 22 are differential amplifier circuits. It is comprised so that it may input to the calculation circuit 23 comprised from etc.

In such an optical disk apparatus, the laser light emitted from the laser diode 11 enters the polarizing beam splatter 13 through the collimator lens 12. Part of the laser light transmitted through the polarization beam splatter 13 is converted into circularly polarized light through the quarter wave plate 14, and is then condensed on the optical disk 20 by the objective lens 15. The laser beam is modulated by the recording information of the optical disc 20. The modulated laser beam passes through the objective lens 15 and the quarter wave plate 14 again, and the quarter wave plate. Returned to linearly polarized light at 14, it enters the polarization beam splatter 13 and is reflected at the polarization splitting surface of the polarization beam splatter 13. The laser light reflected by the polarization splitting surface is incident on the signal reproduction receiver 17 through the condenser lens 16, and is converted into an electrical signal by the signal reproduction receiver 17.

A part of the laser light emitted from the laser diode 11 is reflected by the polarization splitting surface of the polarization beam splatter 13 and is incident on the light receiver 18 for light source monitor. The laser light incident on the light source monitor receiver 18 is converted into an electrical signal.

The optical signal detected by the signal reproduction receiver 17 and the light source monitor receiver 18 is converted into an electrical signal, and each of the electrical signals has the same noise level by the respective amplifiers 21 and 22. After being amplified to a low level, the arithmetic circuit 23 outputs an LNC signal that cancels the laser noise component from the RF signal.

The light emitting mode of the laser diode 11 has two modes, TE mode and TM mode, and these generate noise regardless of each other. For this reason, in the optical head of a non-polarization system, the above-mentioned ratios are the level of the component corresponding to the TE component of the laser beam received by the signal receiving receiver 17 and the level ratio of the component corresponding to the TM component. The first polarization component level ratio is different from the second polarization component level ratio, which is the level ratio of the component corresponding to the TE component of the laser light received by the light source monitor receiver 18 and the component ratio corresponding to the TM component. Therefore, there exists a problem that the cancellation amount of a laser noise falls.

In order to solve this problem, in the present embodiment, the first polarization component level ratio at which the laser beam received by the signal reproducing receiver 17 is received from the laser diode 11 via the polarization beam splatter 13 as an optical separation element, The second polarization component level ratio at which the laser light received by the light source monitor receiver 18 from the laser diode 11 passes through the polarization beam splatter 13 is matched with each other or the difference between the first and second polarization component level ratios. The laser noise component and the light source monitor that adjust the transmittance and reflectance of the polarized beam splatter 13 with respect to the S polarization and the P polarization so as to fall within a predetermined allowable range, and then receive the signal from the receiver 17 for signal reproduction after the adjustment. By taking a difference from the laser noise component received by the light receiver 18, it is possible to obtain a reproduction signal in which a desired amount of laser noise is canceled out. Hereinafter, the detail is demonstrated with reference to FIG.

In FIG. 2, the vector 31 represents the laser noise component of the amplitude 1 received by the signal reproduction receiver 17, and the vector 32 represents the amplitude (received by the light receiver 18 for the light source monitor). The laser noise component of 1) is shown.

In addition, in FIG. 2, (alpha) and (beta) which show the component ratio of TE and TM can be represented by the following formula | equation.

Here, LDp corresponds to the polarization ratio (TE / TM) of the level of the TE component emitted from the laser diode 11 and the level of the TM component, and RFp corresponds to the TE component of the laser light received by the signal reproduction receiver 17. The above-mentioned first polarization component level ratio (TE / TM), FPDp, which is the level of the component and the level ratio of the component corresponding to the TM component, FPDp is a component corresponding to the TE component of the laser light received by the light receiver 18 for light source monitor. The above-mentioned second polarization component level ratio (TE / TM), which is the level ratio of the component corresponding to the TM component and the TM component, and RFpo are on the optical path between the laser diode 11 and the signal reproduction receiver 17. Component corresponding to the TE component of the laser beam from the laser diode 11 to the signal reproduction receiver 17 determined by the optical element including the polarizing beamsplatter 13 and the quarter wave plate 14 present. The above is the ratio of the transmittance of the component corresponding to the transmittance and TM component The first polarization component transmittance ratio (TE / TM), FPDpo is formed by an optical element including a polarizing beamsplatter 13 existing on an optical path between the laser diode 11 and the light receiving monitor receiver 18. The above-mentioned second polarization component transmittance ratio which is the ratio of the transmittance of the component corresponding to the TE component of the laser light from the laser diode 11 to the light source monitor receiver 18 to be determined, and the transmittance of the component corresponding to the TM component. (TE / TM).

If the magnitudes of the laser noise components received by the signal reproduction receiver 17 and the laser noise components received by the light source monitor receiver 18 are matched to take the difference, as shown in FIG. Residual laser noise (NE), TM residual laser noise (NM), and total residual laser noise (NT) satisfy the following equation.

However, θ = α-β.

Here, when the laser noise cancellation amount Na required is known, it is necessary for the laser noise cancellation amount Na to satisfy the following equation.

However, the laser noise cancellation amount Na is represented by the ratio (laser noise level after laser noise cancellation / laser noise level before laser noise cancellation) between the laser noise level after laser noise cancellation and the laser noise level before laser noise cancellation.

Moreover, when this Formula (8) is modified by Formula (3) and Formula (4), it becomes as follows.

That is, the expression (9) is the first polarization of the laser beam received by the laser diode 11 through the optical system including the polarization beam splatter 13 and the quarter wave plate 14. The component level ratio RFp and the second polarization component level ratio FPDp of the laser light received by the light source monitor receiver 18 from the laser diode 11 via the polarization beam splatter 13 coincide with each other or are the first. And the transmittance and the reflectance for the S-polarized light and the P-polarized light of the polarizing beam splatter 13 so that the difference between the second polarization component level ratios RFp and FPDp falls within a predetermined allowable range. That is, the expression (9) can be established to obtain a reproduction signal in which a desired amount of laser noise is canceled out.

For example, in FIG. 1, the transmittance | permeability (Tp) of P polarization | polarized-light which is the polarization characteristic of the polarization beamsplatter 13 especially, Tp = 90%, the reflectance (Rp) of P-polarization Rp = 10%, and the transmittance | permeability of S polarization | polarized-light. When (Ts) is Ts = 0% and the reflectance (Rs) of S polarized light is Rs = 100%, the light quantity ratio received by the signal reproduction receiver 17 and the light source monitor receiver 18 Although the first and second polarization component level ratios RFp and FPDp are both TE: TM = 10: 0 (when TE is aligned in the S direction), the amplifiers 21 and 22 at the rear end are different. By adjusting the noise level, the noise can be completely canceled. Here, since polarization characteristics of optical elements other than the polarization beamsplatter 13 are generally small compared with the polarization beamsplatter 13, it was judged to be negligible.

Next, from the amount of laser noise cancellation required and the first polarization component transmittance ratio RFpo of the optical system from the laser diode 11 to the signal reproduction receiver 17 through the polarization beam splatter 13. The obtained value) is explained. In this case, in (8)

The second polarization component transmittance ratio (FPDpo) can be obtained from equations (4) and (10).

For example, LDp = 100 (TE: TM = 100: 1), RFpo = 1 (TE: TM = 1: 1), and the amount of laser noise cancellations (Na) required was 20 dB (1/100). When obtaining the second polarization component transmittance ratio (FPDpo) at the time, applying the conditions given in the above expression (3),

Substituting the conditions of α and Na into this formula (10),

Β can be represented by this (4),

TE and TM components are all positive values,

20 dB or more of laser noise cancellation is possible by setting the second polarization component transmittance ratio (FPDpo) to a value of 0.5 or more.

In addition, the setting conditions of such an optical system are determined by the polarization beam splatter 13.

(2) Example 2

Next, another embodiment of the present invention will be described with reference to FIG.

In FIG. 3, the same code | symbol is attached | subjected to the same component as FIG. 1, the description of the structure is abbreviate | omitted, and a part different from FIG.

In the other embodiments, the difference from FIG. 1 is that a polarizing element which passes either one of the TE component and the TM component of the laser light emitted from the laser diode between the laser diode 11 and the polarization beam splatter 13 ( 19) is installed.

In this way, the polarization element 19 passes only one polarization component (for example, TE wave component) emitted from the laser diode LDll so that the first and second polarization component level ratios RFp and FPDp are passed. Can be set to TE: TM = 10: 0 as in the case of Example 1.

When the amount of laser noise cancellation required is known in advance, the first and second polarization component level ratios (RFp,) of the laser beams received by the signal reproduction receiver 17 and the light source monitor receiver 18 are also known. It is not necessary to completely match the FPDp), and the difference between the first and second polarization component level ratios (RFp, FPDp) within the error range obtained from the required cancellation amount based on equations (9) and (10) It is good to suppress it.

Also, by adjusting the gains of the amplifiers 21 and 22, when the amplifiers 21 and 22 match the noise level of the RF signal and the FPD signal, the magnitude of the noise level (effective component of noise) is monitored and matched. Let's do it. At this time, the polarization ratio LDp which is the ratio of the level of the TE component and the TM component of the laser light emitted from the laser diode 11 and the optical path between the laser diode 11 and the signal reproducing receiver 17 The first ratio is the ratio of the transmittance of the component corresponding to the TE component of the laser light from the laser diode 11 to the signal reproduction receiver 17 and the transmittance of the component corresponding to the TM component, which are determined by the optical elements present. If the polarization component transmittance ratio RFpo is known, the laser diode determined by the optical element which exists on the optical path between the laser diode 11 and the light-receiving receiver 18 from the required noise cancellation amount Na. The second polarization component transmittance ratio (FPDpo), which is the ratio between the transmittance of the component corresponding to the TE component and the transmittance of the component corresponding to the TM component, from (11) to the light source monitor receiver 18 can be obtained. have.

In addition, although the polarization ratio is adjusted by the polarization characteristic of a polarizing beam splatter in the above-mentioned explanatory example, even if a polarization ratio is adjusted by another optical component, there is no influence on operation | movement. In addition, although the above description is based on the LNC which is a subtraction method, the same effect can be expected with respect to the existing multiplication method in JP 2002-183970 A.

Industrial Applicability The present invention can be widely applied to various optical disc apparatuses having an optical separation element for distributing laser light from a laser light source toward an optical disc and a light source monitor receiver, and reflecting the reflected light from the optical disc toward a signal reproduction receiver. .

Claims (6)

A laser light source, a signal reproduction receiver for receiving reflected light from the optical disk of laser light irradiated to the optical disk from the laser light source and converting the light into an electrical signal, and a light source monitor receiver for detecting the laser light from the laser light source. And an optical separation device for distributing the laser light from the laser light source toward the optical disc and the light source monitor receiver, and simultaneously reflecting the reflected light from the optical disc toward the signal reproduction receiver. A first ratio of a level corresponding to a TE component of the laser light that receives the reflected light from the optical disk from the laser light source through the optical separation element in the signal reproduction receiver and a level ratio of a component corresponding to a TM component Polarization component level ratio of the component corresponding to the TE component and the TM component level corresponding to the TE component of the laser light that receives the laser light from the laser light source through the optical separation element in the light source monitor receiver The transmittance and reflectance for the S-polarized and P-polarized light of the optical separation element are adjusted so that the second polarization component level ratios, which are level ratios, coincide with each other or the difference between the first and second polarization component level ratios is within a predetermined allowable range, , By making a difference between the laser noise component received by the signal reproduction receiver after the adjustment and the laser noise component received by the light source monitor receiver, a reproduction signal in which a desired amount of laser noise is canceled can be obtained. An optical disk device, characterized in that configured to. The method of claim 1, The required value of the laser noise cancellation amount (Na) is represented by the following relationship so that the difference between the first and second polarization component level ratios is within the allowable range.

only, Na: Noise level after laser noise cancellation / Noise level before laser noise cancellation LDp: ratio of the level of the TE component of the laser beam emitted from the laser light source to the level of the TM component RFpo: Corresponds to the TE component of the laser beam from the laser light source to the signal reproduction receiver, which is determined by the optical separation element existing on the optical path between the laser light source and the signal reproduction receiver. The ratio of the transmittance of the component to be transmitted and the transmittance of the component corresponding to the TM component FPDpo: Corresponds to the TE component of the laser beam from the laser light source to the light source monitor receiver, which is determined by the optical separation element existing on the optical path between the laser light source and the light source monitor receiver. The ratio of the transmittance of the component to be transmitted and the transmittance of the component corresponding to the TM component The method of claim 1, And the optical separation element is a polarization beam splatter. The method of claim 1, The optical separation device, The transmittance for the S-polarized light is 0%, the reflectance for the S-polarized light is selected to 100%, the transmittance for the P-polarized light is 90%, and the reflectance for the P-polarized light is set to 10%. An optical disk device, characterized in that. A laser light source, a signal reproduction receiver for receiving reflected light from the optical disk of laser light irradiated to the optical disk from the laser light source and converting the light into an electrical signal, and a light source monitor receiver for detecting the laser light from the laser light source. And an optical separation device for distributing the laser light from the laser light source toward the optical disc and the light source monitor receiver, and at the same time reflecting the reflected light from the optical disc toward the signal reproduction receiver. , Between the laser light source and the optical separation element, a polarizing element for passing one of the laser light TE component and TM component emitted from the laser light source is provided, A level of a component corresponding to a TE component of the laser beam that receives the reflected light from the optical disk from the laser light source through the optical separation element by the polarizing element in the signal receiving receiving element, and a component corresponding to a TM component. The first polarization component level ratio, which is a level ratio, and the TE component of the laser light that receives the laser light from the laser light source and the reflected light from the optical disk through the optical separation element in the light source monitor receiver. S of the optical separation element so that the second polarization component level ratios, which are the level of the component and the level ratio of the component corresponding to the TM component, coincide with each other or the difference between the first and second polarization component level ratios is within a predetermined allowable range. Adjust the transmittance and reflectance for polarized light and P-polarized light, The laser noise component received by the signal reproducing light receiving element after the adjustment is made different from the laser noise component receiving by the light receiving monitor receiver, so that the reproduction signal in which the laser noise is canceled can be obtained. Optical disk device. The method of claim 5, And the optical separation element is a polarization beam splatter.

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